The invention refers to a procedure and device for the assistance of natural spontaneous respiration as well as implementation of mechanical ventilation by recording electrical impedance in the area of the neck and chest, which is influenced by heart action and blood circulation, as well as for controlling a respirator with information derived from electrical impedance measurements.
The assistance of natural spontaneous respiration and substitution of natural spontaneous respiration by respirators is an important factor for resistance and efficiency of an organism under extreme conditions i.e. altitude physiology, deep sea diving medicine, aviation and space medicine. Artificial ventilation (i.e. mechanical ventilation) assists and replaces functions of spontaneous respiration and guarantees a vital oxygen demand of organs and transportation of metabolic carbon dioxide.
In a natural inspiring organism a negative thoracic pressure is produced by movements of the diaphragm and ribs, the consequence of which breathed air flows into the lungs. In artificial ventilation, inspired air is moved from the outside into the lungs by a higher pressure during an inspiration period. In assisted ventilation the pressure difference generated by the movements of the ribs and diaphragm--negative pressure in the thorax cavity--is reinforced by a higher outward pressure built up by a respirator.
The assistance of natural breathing by respirators requires a sophisticated control of the respirators, whereas a quality of this type of ventilation depends essentially on adaptation of a respirator control system to spontaneous breathing intended by the ventilated person. Mechanical ventilation using an intermittent positive pressure (intermittent positive pressure ventilation IPPV) during inspiration period changes the pressure and circulation conditions which are present in spontaneous breathing persons. Versprille et al. shows, that in mechanical ventilation, cardiac output decreases significantly during the insufflation of breathing volume. In the same way pulmonary perfusion and the veneous return via the upper and lower vena cava is afflicted by the pressure changes in the thoracic cavity.
From the impedance curves, measurable in the area of the chest, information concerning cardiac output, ejection and filling time of the heart, valve function, myocardial work, and the thoracic blood, air and fluid content can be derived depending on the placement of current and measuring electrodes.